Fuel cell power plants are well known and are commonly used to produce electrical power from hydrogen containing reducing fluid fuel and oxygen containing oxidant reactant streams to power electrical apparatus such as generators and transportation vehicles. In fuel cell power plants of the prior art, it is known that contaminants may be adsorbed by electrodes of the fuel cells of the plant thereby degrading performance of the power plant. In particular, it is known that hydrogen sulfide is common in various hydrogen fuels and upon passing through a fuel cell becomes an anode catalyst poison. Even very small concentrations of hydrogen sulfide will cause severe fuel cell performance loss over time. Other known contaminants include ammonia, and organic compounds of “direct antifreeze solutions” such as compounds disclosed in commonly owned U.S. Pat. No. 6,316,135, that also become adsorbed by fuel cell electrodes.
Known methods of removing contaminants from fuel cells include passing a liquid removal substance such as an organic solvent, a peroxide or ozonated water through the fuel cell when the fuel cell is not operating, as disclosed in U.S. Pat. No. 6,358,639 that issued on Mar. 19, 2002 to Oko et al. Such a method however, necessarily involves use of complex and costly liquid pumping and valve systems and a significant interruption of operation of the fuel cell. U.S. Pat. No. 6,299,996 that issued on Oct. 9, 2001 discloses use of a system having three valves for switching fuel cells of the system from a first operational state wherein fuel passes through anode flow field plates to a second operational state wherein an oxidant gas supply flows through the anode flow field plates. This system also requires several complicated valves with multiple positions and elaborate flow paths.
Accordingly, there is a need for a decontamination procedure that can efficiently remove contaminants from fuel cell electrodes without requiring extensive interruption of operation of the fuel cell power plant and that does not require costly, complex valve and flow path apparatus.